small letters

I think what you are describing is dry transfer lettering.  It used to be common, found in office and art supply stores.  I understand that some art stores still have a limited supply.  The personal computer and graphics and word processing have basically killed the office market.

They are still available.  Do a Google search for "dry transfer lettering."  Archer, one brand, seems to have discovered model makers, and I think products aimed at modelers has become a more significant market for that company.

  The just-plain-letters are available in three or four fonts, and black, white, or gold colors, in several sizes.

Don't buy older "remaindered" sets of dry transfer letters. I still have boxes of them from Architecture school, 35 years ago. They go bad.

Woodland Scenics the landscape material company makes a pretty comprehensive line. The ones I've bought seem fresh.

Don, you'd appreciate this. I've found a pretty good LHS since I moved last year. Like most, they do a lot of RC car stuff to keep afloat. Someone once was an owner who really understood the hobby as much more than plastic kits. The other day I was looking for some decals of white stars. As they have gotten to know me, I got the "sure go behind the counter and look" treatment.

I found a back room FULL of filing cabinets of large scale RC aircraft markings and decals. Drawers of the stuff. National insignia you couldn't span with your fingers spread wide.

Oh, and shelves of old ship model kits. But that's another story. Lots of RC lake sailers though.

One of my recurring "good" dreams is to dream about finding a hobby shop that has all sorts of wonderful stuff, especially real old models that I lusted after as a kid, but could not afford, like those gas-powered tether race cars (pre-RC stuff).  Also old "solid model" wood scale aircraft kits.